Transmit-receive tube



Filed April 23, 1956 FIG. I

H. c. ALEXANDER ETAL' 2,918,603

TRANSMIT-RECEIVE TUBE 2 Sheets-Sheet 1 INVENTOR5 HERBERT C. ALEXANDER JOHN E. BURR JR.

ATTORNEY Dec. 22, 1959 H. c. ALEXANDER F-TYAL 2,918,603

TRANSMIT-REGEIVE was Filed April 23, 1956 2 Sheets-Sheet 2 32 l I I 5 /,6

:IT |6 I 9 I 3 I I- r|a 1 2a I I 27 S I- I x I I9 I I 39 1 as 20 a? F|G.2

INVENTORS HERBERT c. ALEXANDER an E. BURR JR.

JO BY J k ATTORNEY United States Patent TRANSMIT-RECEIVE TUBE Herbert C. Alexander, Peabody,

Wenham, Mass.; Laboratories Inc., Massachusetts and John E. Burr, Jr., said Alexander assignor to Bomac Beverly, Mass, a corporation of The present invention relates to gaseous discharge switching devices and more particularly to a novel transmit-receive tube.

Generally such tubes are employed in radio direction and ranging systems to permit the use of a common antenna for transmission and receiving. Examples of the various embodiments may be seen in United States Patent No. 2,724,791 issued to George E. Carter, Jr. and assigned to the assignee of the present invention, as well as United States Patent No. 2,678,408 issued to Louis W. Roberts. Prior art TR tubes, commonly employ a differential tuning mechanism to tune to a specific resonant frequency; an ignitor electrode to facilitate breakdown of the ionizable atmosphere contained within the enclosure and an exhaust tubulation to permit evacuation of the internal atmosphere and filling with an ionizable gas under reduced pressure. These components are mounted in their respective positions now well known in the art.

With the advent of the combination of a TR and attenuating device as shown in United States Patent 2,734,171 issued to Harold Heins and assigned to the present assignee, the space formerly occupied by the ignitor electrode has been utilized for the electromechanical structure to activate the attenuator member. This resulted in the so-called side-arm ignitor electrode shown in the cited reference.

To further improve the state of the art and to simplify fabrication problems, we have discovered a unique structure for TR tubes in which the ignitor electrode and exhaust tubulation are an integral unit introduced through the tuning mechanism of the tube.

It is an object of the present invention to provide a novel transmit-receive switching device incorporating in the differential tuning mechanism an ignitor electrode and exhaust tubulation as a unitary structure.

. .It is a further object to provide means for tuning, igniting and exhausting a transmit-receive tube with said components being introduced therein at only one endof the tube envelope.

Referring now to the drawings for a more detailed description of the invention; Figure 1 is a cross-sectional view of a selected embodiment of the invention and Figure 2 is an enlarged detailed view of the components utilized for tuning, exhausting and igniting the selected embodiment.

The transmit-receive tube shown generally at 1 comprises a cylindrical conductive enclosure member 2 provided with an axial passage 3 therethrough. Positioned within the central portion of said passageway are spaced hollow discharge gap conical electrodes 4 and 5 with the broad walls 8 and 9 thereof hermetically sealed to the passageway walls and defining therebetween a resonant cavity 6. Window 7 centrally located in member 2 provides means for transmission of electromagnetic wave energy through the tube. An inert ionizable gaseous atmosphere such as argon or hydrogen with a small perecntage of water vapor is retained within the cavity 6 to 2,918,603 Patented Dec. 22, 1959 2 provide for a gaseous discharge when the threshold voltage presented at window 7 is attained.

In the selected embodiment the attenuator mechanism occupies one end of the passageway 3 with an attenuator rod 10 extending into hollow electrode 4% to contact opposed electrode 5 when in full attenuating position. Electromechanical activating means 11 and a spring 12 communicate with attenuator member 10 in accordance with the teachings of the aforementioned United States Patent 2,734,171. A more complete description will therefore be omitted in this specification.

Since the attenuator mechanism occupies the end of the axial passageway it has been customary in the art to introduce the keep-alive or ignitor electrode through wall 13 of passageway 3"While the exhaust tubulation could be positioned in the opposed wall 14. Additional time is required to assemble these components and a problem exists in the positioning of the sidearm ignitor electrode in determining the proper spacing from electrodes 4 and 5 to assure partial ionization of the gaseous atmosphere. Generally the individual skill of the operator must be relied upon to attain this accurate positioning.

We have provided, therefore, a simplified structure embodying the ignitor electrode and exhaust tubulation, as an integral structure within the tuning mechanism which may be fabricated as a sub-assembly shown generally at 15 and introduced at the opposite end of passageway 3. The specific details will now be described with reference to Figure 2.

Conical electrode 5 which is axially movable with respect to opposed electrode 4 to alter the resonant frequency of the tube has a central hub portion 16 and a broad wall 9 with a deformable. diaphragm portion 17 formed therein in the manner well-known in the art. Secured to hub portion 16 is an elongated tubular member 18 which extends outside the tube envelope 2 and is provided with a threaded portion 19 at an intermediate point thereof. Collar 20 is then hermetically sealed to the outer end of tubular member 18. In the method of fabricating the tube, components 5, 16, 18 and 20 may be brazed together in a hydrogen furnace to provide at hermetically sealed enclosure in one operation.

The ignitor electrode comprises a conductive rod 21 having a hollow metallic exhaust tubulation 23 joined at one end thereof as by brazing or soldering. An insulating sheath 22 extends over the lateral surfaces of the rod 21 and a portion of the joint of the tubulation 23. An aperture 24 is provided in tubulation 23 to permit evacuation of the internal atmosphere of the device.

The tuning mechanism of the complete tube is of the differential threaded type Well-known in the TR tube art and. comprises a tuner cylinder 25 internally threaded and adapted to enclose an end of passageways. Set screws 26 and 27 firmly maintain this cylinder in its desired position. Differential tuner screw 28 having a substantially fiat broad wall section 39 is provided with a screw thread on one surface to mate with the tuner cylinder while the inner thread is complementary to the threaded portion 19 of tubular member 18. Spring 30 and a cup washer 31 are internally mounted within the passageway 3 and are in contact with hub portion 16 of cone 5.

The ignitor electrode 21 together with metallic exhaust tubulation 23 is positioned within tubular member 18' with the inner end extending into a transverse aperture 32 near the apex of cone 5. This facilitates the introduction of electrons into the discharge gap region to permit partial ionization of the gaseous atmosphere. This assembly may then be positioned by means of glass head 33 secured to collar 20 and tubulation 23.

In the method of fabricating the described embodiment the tuning mechanism may be mounted simply by insert ing washer 31 and spring 30 in their respective positions, inserting cylinder 25 into the envelope passageway and anchoring same by means of set screws 26 and 27. Tuner screw 28 may then be positioned by means of theinner threads of cylinder 25 and the threaded portion 19 of tubular member 18 which has already been prebrazed to the electrode 5 assembly.

The ignitor electrode with its appended exhaust tubulation may then be positioned within tubular member 18 and sealed to collar 20 by means of glass bead 33. Suflicient clearance is allowed to provide a passage 34.

Evacuation of the internal tube atmosphere will now be carried out by connection of tubulation 23 to an exhaust system. It will be noted that passage 34 communicate's with aperture 32 to thereby provide for evacuation of the internal atmosphere. Aperture 24 in tubulation 23 provides the means for communicating with passage 34 to complete the flow. After the reduced atmosphere desired has been attained and a suitable ionizable atmosphere introduced, exhaust tubulation 23 is sealed off as at 35 to provide a vacuum tight enclosure. A top cap 36 with a suitable aperture to accommodate exhaust tube 23 is then cemented to glass bead 33 and the outer surfaces may be dip soldered as at 37. A cylindrical protector sleeve 38 may then be secured to wall 39 of tuning screw 28 to prevent any damage to the overall assembly outside the tube envelope. A suitable direct current voltage supply may then be electrically connected to top cap 36 to provide a source of electrons in the area of the tip of electrode 5 to thereby partially ionize the gaseous atmosphere.

To explain the operation of the method of tuning the illustrative embodiment, Figure 2 shows the position of the electrodes 4 and 5 after the attenuator rod has been removed and normal transmit-receive action is desired. In this view the tuning mechanism has been rotated to the limit or depth of insertion of the tuner screw 28 which means that the two electrodes are almost in contact. By rotating sleeve 38, which may be employed as a tuner knob in a counter-clockwise manner, screw 28 moves axially away from the outer walls of cylinder 25. Since dilferential threads are employed, a larger number of turns of screw 28 are necessary to reflect a small change in threaded portion 19 of member 18. Since this member is securely attached to cone 5 and the electrode-exhaust tubulation combination is secured to the member at 33, the movement of cone 5 will be effected to thereby widen the gap to tune to the higher end of the tuning range. The distance of electrode 21 from the apex of cone 5, however remains constant throughout the axial movement of member'18. This advantage is of considerable importance in the transmit-receive tube electrical characteristics since the space of the electrode 21 from the tip of its adjacent cone electrode structure governs the degree of partial direct current ionization present in the tube before the main radio frequency energy gaseous discharge.

There is thus disclosed a transmit-receive tube which may be fabricated with fewer operations at a saving in cost of manufacture and lends itself to the incorporation of other desirable components in the areas formerly occupied by the ignitor electrode and exhaust tubulation. For example, a heater and thermostat combination in addition to the shutter mechanism may be mounted against the passageway walls 13 and 14 as explained in the copending application Serial No. 580,083 filed by Harold C. Booth and assigned to the present assignee.

While a specific embodiment has been described, other modifications or alterations may occur to skilled artisans. Hence, it is our intention to cover in the appended claims all such modifications or alterations as fall within the spirit and scope of the invention.

What is claimed is:

l. A transmit-receive tube comprising a conductive cylindrical enclosure having an axial passageway therethrough, a pair of opposed conical electrode centrally positioned within said passageway, a differential tuning assembly enclosing one end of said passageway to control movement of one of said electrodes, said tuning assembly having an internally threaded passage therethrough and an external rotatable member, an elongated tubular member extending into said enclosure through said threaded passage with an intermediate portion thereof being in threaded engagement with the passage threaded walls, said tubular member being hermetically sealed at its inner end to said movable electrode, an ignitor electrode having a sheath of an insulating material disposed on its lateral surfaces and a metallic exhaust tubulation'secured thereto at one end, said ignitor electrode and exhaust tubulation extending into said enclosure through said elongated tubular member with the tip of said electrode terminating at a point adjacent to the apex of said movable electrode, a metallic collar secured to the outer end of said tubular member and joined to said ignitor electrode and exhaust tubulation by means of a glass-to-metal seal, said movable electrode together with the ignitor electrode and exhaust tubulation being adjustable in unison as said tube is tuned during operation by means of said external rotatable member.

2. A transmit-receive tube according to claim 1, wherein the distance between the inner tip of the ignitor electrode and the apex of the movable electrode remains fixed throughout the axial displacement of said tuning assembly.

References Cited in the file of this patent UNITED STATES PATENTS 2,524,268 McCarthy Oct. 3, 1950 2,734,174 Heins Feb. 7, 1956 2,746,017 Lawson May 15, 1956 2,773,215 Miller Dec. 4, i956 2,819,425 Dutt Jan. 7, 1958 UNITED STATES PATENT 'O'FFIE CERTIFICATE OF CORRECTION Patent No. 2,918,603 December 22, 1959 Herbert 0., Alexander et a1.

requiring correction and that the said Letters Patent should read as corrected below,

In the grant, lines 2, 3 and 4, for "said Alexander assignor to Bomac Laboratories, Inc., of Beverly, Massachusetts, a corporation of Massachwsetts," read assignors to Bomac Laboratories Inc. of Beverly, Massachusetts, a corporation of Massachusetts, lines 13 and 14, for "John E; Burr, Jr., his heirs or assigns, Bomac Laboratories, Inc., its successors" read Bomac Laboratories Inco its successors in the heading to the printed specification, lines 4, 5 and 6, for "said Alexander assignor to Bomac Laboratories l'ncn Beverly, Mass,, a corporation of Massachusetts, read w assignors to Bomac Laboratories Inc Beverly, Masts a corporation of Massachusetts Signed and sealed this 24th day of May 1960..

(SEAL) KARL H, AXLINE ROBERT c, WATSON Attesting Officer Commissioner of Patents 

